Developing unique nanoporous titanate structures for biomedical applications: mechanisms, conversion and substitution

Titanate structures have been of interest in many sectors, including healthcare, due to their ease of manufacture (low processing temperature and simplistic equipment), ion exchange potential to produce multifunctional (bioactive and antibacterial) surfaces, as well as their nanoporosity. However, their use has been limited to only Ti-containing materials due to the specific wet chemical methodology employed. The work presented in this thesis demonstrates one of the first studies to generate gallium-doped titanate structures as a multifunctional surface, specifically to assess their cytocompatibility and antibacterial potential for biomedical applications. Successive wet chemical (5 M NaOH; 60 oC; 24 h), ion exchange (4 mM Ga(NO3)3; 60 oC; 24 h), and heat treatment (700 oC; 1 h) stages were employed on Cp-Ti surfaces. Gallium was shown to be fully incorporated (ca. 9 at.%) into the nanoporous titanate structure, and completely replaced sodium (initial Na content ca. 3 at.%). The heat treatment stage crystallised the amorphous titanate layer, which increased the stability and reduced the maximum level of Ga3+ released (ca. 2.76 vs. 0.68 ppm for pre- and post-heat treated gallium titanate samples, respectively) into DMEM over 7 d. Finally, the heat-treated gallium titanate samples were shown to be cytocompatible, compared to the non-heat-treated samples, which demonstrated a significant (p < 0.0001) reduction compared to the TCP control. Unfortunately, neither gallium titanate samples exhibited robust antibacterial properties against S. aureus. The applicability of titanate structures was furthered in this thesis through the optimisation and characterisation of novel wet chemical (5 M NaOH; 60 oC; 24 h) titanate-converted Ti thin films deposited via DC magnetron sputtering. The films produced were deposited onto 316L SS to function as thin coatings for orthopaedic applications. This was in lieu of the ‘gold standard’ plasma sprayed hydroxyapatite (HA) coatings, due to